Most of my mileage is motorway, I don't particularly take it easy as I get paid a good rate for it so my speed is normally limited by traffic flow and I like to "make reasonable progress" when getting up to speed but I normally get between 55-60 indicated MPG which in reality is around 5MPG optimistic (around 10%)

As I don't drive everyday (work from home) we've decided to have a primary and secondary car so my wife is now using it also, her driving is more A road so MPG is around 50 indicated / 45 actual.  But as the other car has a 5.5L V8 petrol engine this is still cheaper.

 

I'm disappointed in the maxidot accuracy but then we do know what kind of relationship VW has with the truth don't we?

Other than that I don't really care, personally I think this is not bad going for a large car and slightly better than my previousl car which I had no complaints about. I only really keep an eye on it in case it suddenly changes which may indicate a problem.

Mine is a 2008 140BHP car which will be the pre-CR engine I believe.  Don't know if this is better or worse than later engine for MPG and even though it's only a 140 (and I like my powerful vehicles) I actually like the power delivery.

 

 

On my 1.4 tsi petrol the mpg display is surprisingly accurate compared to tank to tank measurements. Is it measured differently?

 

On my previous Superb I 1.9 the display seemed to get more and more pessimistic as the car became older and the miles piled on - It started a little optimistic at 18k miles and was 4mpg pessimistic  when I sold it to a friend at 163k miles 10 years later.

 

Edited 5 October, 20187 yr by bigjohn

On the accuracy of the dashboard computer, my 170 diesel is also optimistic - usually by 2 - 3 mpg.

This surprised me when I first checked it in as my previous car it was spot on, accurate to a tenth or two mpg compared to calculation. That car was a SEAT with the old 1.9l 130 HP "PD" diesel. Hard to understand why the modern version should be so much worse without thinking of conspiracy theories!

55 minutes ago, MikeHig said:

On the accuracy of the dashboard computer, my 170 diesel is also optimistic - usually by 2 - 3 mpg.

This surprised me when I first checked it in as my previous car it was spot on, accurate to a tenth or two mpg compared to calculation. That car was a SEAT with the old 1.9l 130 HP "PD" diesel. Hard to understand why the modern version should be so much worse without thinking of conspiracy theories!

I have wondered if the include the extra fuel they use for DPF regeneration on the display. This would also explain why petrol engine cars don't suffer so much.

44 minutes ago, Gdcobra said:

I have wondered if the include the extra fuel they use for DPF regeneration on the display. This would also explain why petrol engine cars don't suffer so much.

It would be hard for it not to.

32 minutes ago, chimaera said:

It would be hard for it not to.

Why? The ECU knows what extra it is adding it would be simple for a computer to exclude it's extra in its MPG  calculation and I guess the argument would be that this fuel is not being used to provide miles but a cleaning service.

1 hour ago, Gdcobra said:

Why? The ECU knows what extra it is adding it would be simple for a computer to exclude it's extra in its MPG  calculation and I guess the argument would be that this fuel is not being used to provide miles but a cleaning service.

 

Depends where it is being measured and how. 

 

I remember having a device a few years ago long before on board computers that was an add on mpg meter that that a flow meter and a magnet on the prop/sensor. The problem was some fuel was returned to the tank so it was hard to calibrate and measure the true usage - got fairly close though.

 

Fast forward to today and the modern common rail diesels will have about three sources of fuel return (I think ) - one from the low pressure return from the injectors and one from the CR pressure relief and one from the pump itself (I think it's something to do with lubrication) - so It's probably difficult to be accurate. Suspect it's calculated by an estimate of what the injectors are being told to do (inc regens).

 

Direct injection petrol is different again. 

2 hours ago, Gdcobra said:

Why? The ECU knows what extra it is adding it would be simple for a computer to exclude it's extra in its MPG  calculation and I guess the argument would be that this fuel is not being used to provide miles but a cleaning service.

The short answer is because it would require more code in the ECU software.

Embedded systems developers avoid additional code as much as possible because it introduces possibilities for things to go wrong, and if the function is not needed it's not written. Fuel consumption data is measured by the amount of fuel being metered through the injectors: duration of injection along with rail pressure is correlated to fuel use and that data is part of the feedback loop used by the ECU to keep things under control. It's then also used to send fuel consumption information to the instrument panel for presentation to the driver.

Across all brands and models, VAG have consistently programmed the MFD to present better than actual fuel consumption: read back through the last 15-20 years of posts on the various VAG brand enthusiast boards and you'll see it come up time and time again. On average, this discrepancy works out around 15 %: there will be variation due to manufacturing and operating tolerances on individual vehicles. VAG provide a function via diagnostics to adjust the calibration so that it reads more accurately, so it's always possible on a used vehicle that the previous owner had this done, leading to people finding the odd car that's reporting correctly.

 

Bottom line is that more than likely any VAG car will have an incorrect readout of economy on the MFD and if you're unhappy with this, do the work to calibrate it.

2 hours ago, Gdcobra said:

Why? The ECU knows what extra it is adding it would be simple for a computer to exclude it's extra in its MPG  calculation and I guess the argument would be that this fuel is not being used to provide miles but a cleaning service.

Unfortunately, it doesn't matter if fuel is used during driving, when stationary or to "clean" DPF - the moment you start your engine - you burn your fuel. 

 

In "mpg (GB/US), mi" mode you will see "---" as current consumption when coasting or stationary - but if you switch to "l/100km, km" - you'll see "l/h" when stationary and "l/100km" when driving. 

Just throwing it out there guys, seems there are owners with petrol engine claiming good accuracy diesel owners claiming poor. I'm not claiming any knowledge of what's in the box but I'm assuming fuel use is measured by the accumilated injector open time if there is an additional squirt for DPF re-gen this may just nothe get counted. It could arguably require more code to do so.

On the Mazda 6 diesel my wife had the computer was dead on but it was the only thing about that car which I'd praise. To put it into conext we kept a 10 year old Superb (and not even a very pretty one) in preference to a 2 year old Mazda.

Dear all,

Thanks for all the replies. I am not sure the variation in mpg is purely down to driving style. I am wondering if newer engines are better due to design or lack of wear, but just a theory.

Cheers,

  ANdrew

1 hour ago, Goderich said:

Dear all,

Thanks for all the replies. I am not sure the variation in mpg is purely down to driving style. I am wondering if newer engines are better due to design or lack of wear, but just a theory.

Cheers,

  ANdrew

Or maybe worse due to additional emissions twaddle?

Just been out and checked the latest fuel consumption it's 53MPG (probably 48 actual) over the last week/300miles.  In that time I've not driven it, all the miles have been done by my wife, she normally doesn't get such a good figure as she's doing 16 miles a day to work (and the same back home again) just over half of which is motorway.  I'm wondering if the recent change of brake calipers has improved it.  Perhaps they were dragging more than I thought.

I've got a 270 mile trip on Thursday mainly motorway, be interesting to see what that returns.

Filled up last night and did a 273 mile trip today, when I got back MFD was indicating 64MPG, filled up again, took 22L so just over 56MPG in reality. Seems that the MFD is getting even more inaccurate but as I'll net £113 for the trip, can I be bothered?

 

 

 

Petrol tsi Not quite as good as my old Superb I1.9pd100 - but it's not far off!

 

Edited 11 October, 20187 yr by bigjohn

remapped 170 to 200+ DSG 2wd estate average mpg with mixed town driving is around 41-43 motorway  at or below 70 you can get close to 51-55 @70 plus is back down to 46 @100 your at 36-38 (on the autobhan of course) we usually get about 550 miles between refills but to be honest dont worry about it too much

On 27/09/2018 at 18:06, Goderich said:

I have calculated this from 386 miles for 43 litres. It is not the 4 x4. I don't know about brakes dragging, I guess I would have to get a mechanic to look at it. Honest JOhn quoted 46 mpg for real mpg for Mk II Superbs but might include smaller engines.

Just read your figures.  I have a 2-litre superb estate. I get 35-40mpg around town and 50-53mpg on a run. If I stick to 55mph, I can squeeze 65 mpg out of it, but that's driving like a real miser! I have fitted a "GOFAR" to my car which shows you exactly where you are wasting your money.

I get 56 mpg on a daily baisis, which is mostly short country drives, but on a long trip on the motorway I can easily get to 68-70 mpg. My superb is a 2.0 TDI 140hp CR.

Is that what the cars computer says or is that what you have calculated yourself?

 

I ask as my 1.6 TDI 105hp CR tells me similar mpg to yours on its display. A manual calculation (i.e. fill it up, drive till it needs refueling, fill it up again  & calculate what I really got for the miles driven) almost always shows it is 5 mpg or so lower. Its a VAG car - it knows how to tell lies about such things....  

The 41 mpg is based on refilling. The cconsensus seems to be that the MFD lies.

My best tank based on refilling in Ireland was 60 mpg, MID said 65 mpg

(My best tank based on refilling in the UK was 65 mpg, MID said 68 mpg)

My worst tank based on refilling was 44 mpg, MID said 46.5 mpg

My long term consumption over 2.5 years, based on refilling calculation, is 48 mpg. The MID averages would have been 53 mpg. Time spent driving  would be 40% urban, 40% rural or 2 lane roads and 20% motorway.

 

On a separate note - I have been to the UK with my car a few times. I always get a 5 to 6 mpg per tank boost over driving in Ireland. I put that down to the speeds I was kept to (slow but economical) as well as the motorways being busier with far more time spent in SUV/truck/lorries slip streams.

Since I bought mine in May '17 I've been recording MFD average for each tank along with actual economy. After yesterday's refill my data showed that the MFD was an average of 13.7 % better than actual. Using that I adjusted the MFD upward by 14 % using the adaptation channel in the instrument cluster (only whole number adjustment allowed).

 

On a 388 km round trip today (60/40 motorway/A-road) MFD reported 6.1 l/100 km average, about 46.3 mpg.

Edited 23 October, 20187 yr by chimaera

4 hours ago, TheRobinK said:

Is that what the cars computer says or is that what you have calculated yourself?

 

I ask as my 1.6 TDI 105hp CR tells me similar mpg to yours on its display. A manual calculation (i.e. fill it up, drive till it needs refueling, fill it up again  & calculate what I really got for the miles driven) almost always shows it is 5 mpg or so lower. Its a VAG car - it knows how to tell lies about such things....  

That was calculated, my MFD shows 2-3 more mpg 

MFD over-reading by 14% seems about right to me. I wonder if there is another fraudulent software scandal here?

19 minutes ago, Goderich said:

MFD over-reading by 14% seems about right to me. I wonder if there is another fraudulent software scandal here?

Doubtful - they've been doing that for at least the last 20 years.